Building a Large Aerobic System¶
Goal: Develop aerobic capacity, threshold, durability, and neuromuscular power together.
Most training should be easy. Add smaller, targeted doses of high-intensity work.
A typical routine involves about 80% of easy (volume) work with on 20% of quality work.
Training Systems¶
| System | Intensity | Primary adaptation |
|---|---|---|
| Easy aerobic | Z1–Z2 | Mitochondria, capillaries, oxidative capacity, volume tolerance |
| Tempo / Threshold | Z3–Z4* | Sustain a larger fraction of aerobic capacity; lactate processing |
| VO₂ max | Severe | Maximal aerobic power |
| Sprints / Speed | Very high | Power, fast-twitch recruitment, economy |
* Zone definitions vary. Train physiological qualities, not arbitrary zone numbers.
Training Structure¶
No physiological reason exists to fit every stimulus into seven days. A 2-week cycle can reduce crowding of hard sessions.
Typical week:
- 2 quality sessions
- 1 long run
- Remaining running = easy/recovery
| Day | Week 1 | Week 2 |
|---|---|---|
| Sun | Long run | Long run |
| Tue | VO₂ max | Sprints |
| Thu | Threshold | Threshold |
Progress by increasing volume, duration, density, speed, or specificity—not simply by adding more hard days.
Aerobic Base¶
Easy volume builds the underlying aerobic machinery:
- ↑ Mitochondrial capacity
- ↑ Capillarization
- ↑ Fat oxidation
- ↑ Aerobic efficiency
- ↑ Training-volume tolerance
Long Runs¶
Long runs additionally develop durability:
The ability to preserve efficiency, mechanics, and power as fatigue accumulates.
~2 hours / 20 miles can be a practical ceiling for routine long runs, not a physiological law. Longer/back-to-back runs may be appropriate for specific endurance or ultra goals.
For beginners running 20 miles in 2 hours in zone-2 is rather difficult, hence training in 3 hour ceiling is more helpful. With time the pace improves.¶
VO₂ Max¶
VO₂ max = maximum rate of oxygen uptake and utilization.
It is not trained exclusively through sprinting.
Useful stimuli include:
- Longer VO₂-max intervals
- Short repeated intervals
- Hill intervals
- Other severe-intensity work producing substantial time near high oxygen consumption
Example:
4–5 × 30 s very hard / 90 s recovery
This can contribute to VO₂-max development, but strongly stresses anaerobic + neuromuscular systems as well.
A genuinely large aerobic system takes years to develop.
Sprinting might not be a good enough idea especially if we let the HR drop to comfortable levels between intervals as it decreases the aerobic demand on the system. The system needs to be under high aerobic stress for it to develop.
Threshold¶
Threshold work develops the ability to sustain a large fraction of aerobic capacity.
Key adaptations:
- Higher sustainable pace/power
- Better lactate transport and oxidation
- Greater tolerance of prolonged high aerobic demand
Think:
VO₂ max = size of engine
Threshold = fraction of engine you can sustain
Sprints & Speed¶
Sprints primarily develop/preserve:
- Fast-twitch recruitment
- Neuromuscular power
- Force production
- Speed
- Running economy
They complement aerobic training rather than replace it.
Speed Under Fatigue¶
Occasionally:
Long aerobic effort → carbohydrate → 4–5 × ~30 s hard efforts + recovery
Purpose:
- Preserve high-threshold motor-unit recruitment
- Maintain power and mechanics under fatigue
- Rapidly utilize carbohydrate
- Produce high output late in prolonged exercise
The objective is quality under fatigue, not exhaustion.
If mechanics or power collapse, the intended stimulus is largely lost.
Fat vs Carbohydrate¶
The body almost always uses both fat and carbohydrate. Their relative contribution changes with:
- Intensity
- Duration
- Training status
- Fuel availability
Aerobic training itself improves fat oxidation.
Better goal:
Metabolic flexibility = efficiently oxidize fat at lower intensities while retaining rapid carbohydrate utilization when intensity increases.
Avoid deliberately underfueling important sessions solely to maximize fat oxidation.
Fueling¶
Large aerobic workloads require substantial energy availability.
Chronic underfueling can impair:
- Recovery
- Training quality
- Adaptation
For long/hard sessions, carbohydrate intake should scale with workload.
Highly trained athletes with trained GI systems may tolerate approximately:
90–120 g carbohydrate/hour
Carbohydrate availability helps preserve glycogen, pace, power, recovery, and late-session high-intensity output.
Lactate¶
Lactate ≠ metabolic waste.
During hard exercise:
Glycolytic fibers produce lactate → lactate is transported → oxidative tissues consume it as fuel
A strong aerobic system improves this production → transport → oxidation cycle.
This is one reason aerobic capacity remains important at high intensities.
Additional Tools¶
Heat Acclimation¶
Can produce:
- ↑ Plasma volume
- ↑ Sweating response
- Better thermoregulation
- ↓ Cardiovascular strain in heat
Treat heat as additional training stress, not free adaptation.
Sodium Bicarbonate¶
Increases extracellular buffering capacity and can improve performance during sufficiently intense efforts.
Primarily useful for high-intensity work, not aerobic-base development.
Main limitation: GI distress.
Decision: NOT doing this.
Core Model¶
Volume builds the engine.
Easy aerobic work supplies most underlying adaptation.
Threshold increases sustainable output.
Use a larger fraction of the engine for longer.
VO₂-max work raises the ceiling.
Periodically expose the aerobic system to near-maximal demand.
Sprints preserve power.
Maintain recruitment, speed, force, and economy.
Long runs build durability.
Preserve performance as fatigue accumulates.
Late-run intensity combines durability + power.
Produce high output after prolonged aerobic work.
Fuel the work.
Don't sacrifice training quality and recovery for "fat adaptation."
Think in years.
Adaptations appear within weeks; a large aerobic system is built through years of progressive, consistent training.